Loading

About

This map shows the position of almost every known gamma-ray burst (often called GRBs), at least those for
which astronomers have been able to measure a position (GRBs are often detected without any way of
knowing where exactly they came from).
The map is an
equirectangular projection of the night sky
in galactic coordinates,
showing the entire sky as visible from Earth with our Milky Way galaxy running through the middle.
The size of each circle illustrates the relative brightness (as seen from Earth) for each GRB,
and the length of time each circle persists is scaled to 1/20th of the true length of
the burst. Note that many of the earlier GRBs were detected by instruments that were not able to measure
the true brightness or length of the burst - average values are used when showing these bursts on the map.
The slider on top of the page lets you move through history, exploring when different GRBs were
first discovered. Look to the counter in the top right to see what date range is currently shown, and
click on any GRB to learn more about it.

A gamma-ray burst
is a short flash of incredibly high-energy light (gamma-rays). There are two major types,
called long and short GRBs because of the length of time of the burst. Long GRBs are more common
and usually last about 30 seconds, while short GRBs last only an average of 0.3 seconds. Long
gamma bursts seem to be associated with core-collapse supernovae of incredibly massive stars,
also known as hypernovae. In a hypernova,
the core of the star collapses into a black hole and relativistically-beamed jets of gamma-rays
blast out of the exploding star, forming the short and bright bursts we see here on Earth.
Short GRBs are less well-understood, but many researchers believe they could be caused by
the merger of two neutron stars -
exactly what causes short GRBs is an important question that researchers are still working to figure out.

Our atmosphere does not allow gamma-rays through it, which is usually a good thing because it protects
us from their damaging effects. However, it does make it difficult to study GRBs. In fact, the main
tools researchers use to detect GRBs are space satellites, flying far above the Earth's atmosphere. The first GRB was
detected in 1967 by the Vela satellites
which were built by the USA to detect nuclear weapons testing by the Soviet Union (nuclear bombs emit
gamma-rays). The military knew that the bursts they detected were not caused by nuclear testing but did not know
what could be causing them. The early detections were classified until 1973, when the USA made the
first public announcement describing these inexplicable bursts. There have now been several
generations of satellites designed to help study GRBs and we've learned a lot more about them (see
here
for a good summary). The map on this page includes all of the GRBs astronomers have been able to
observe with well-measured positions - right now, that's -- GRBs.

Trends

Because they come from very distant galaxies (which are equally spaced in all directions),
GRBs happen all over the sky. Most of the trends and patterns visible in the animation above are
due to the methods astronomers use to look for and discover GRBs and are not real trends in GRB
properties. For example, early GRB-detecting satellites were not very good at measuring how
long a GRB lasts, and so
the early GRBs are shown with an average duration, while the
more recent GRBs
are shown to fade over a length of time scaled to their true (observed) duration.
Here are a few other interesting trends:

Modern GRB-detecting satellites are more capable than the early satellites, and so
there are more GRBs being detected today than ever before (though the true rate
of GRBs occurring in the universe has not actually changed)

The sensitivity of GRB-detecting satellites (and their ability to identify where a
burst came from) depends strongly on the relative positions of the satellites in orbit. There are a few
times you can identify paths across the sky where satellite configurations were
particularly sensitive; here, for example.

Unlike supernovae, we can detect GRBs through the gas and dust of our Milky Way galaxy.
The gas and dust at the center of our galaxy blocks most of the optical light from supernovae,
but gamma-rays from GRBs pass through with little trouble.

Acknowledgements

This website was built by
Isaac Shivvers, an astrophysics graduate student
at UC Berkeley. Feel free to contact me with any questions or comments at
ude.yelekreb.ortsa@srevvihsi.